(1) Field of the Invention
The present invention relates to an engine arrangement, and in particular relates to an arrangement of a four-cycle engine mounted on a snowmobile.
(2) Description of the Prior Art
Conventionally, small snow vehicles such as snowmobiles have mainly used two-cycle engines. A two-cycle engine is characterized by a relatively simple engine configuration having the advantages of being lightweight and compact and still providing high power. However, two-cycle engines have drawbacks, when compared with four-cycle engines, of emitting a greater amount of exhaust and louder noise with greater vibrations.
The recent worldwide trend demands a silent, clean and environment-conscious engine. Snow vehicle engines are no exception and clean and silent engines have been desired. To fulfil this demand, development of engines for snowmobile into a four-cycle configuration has been studied.
As shown in FIG. 1, a typical conventional snowmobile 200 has a body frame 210 in a monocoque frame configuration, wherein an engine 202 is mounted in a space formed between a track housing 211c and a front suspension housing 211b in the front frame (engine mounting frame) 211. For a two-cycle engine, engine 202 is mounted upright in an engine compartment 206.
If a four-cycle engine is attempted to be put into use for a snowmobile in the same manner as above, the upright mounting has been difficult because a four-cycle engine has a greater full height compared to a two cycle engine due to its bulky cylinder head and the necessity of an oil pan. Further, since a four-cycle engine needs additional parts unique to it such as an alternator, supercharger, intercooler, oil filter and the like, it has been very difficult to lay out all these parts in a limited engine compartment space.
To overcome the above space difficulty, there has been a layout proposal as shown in FIG. 2 in that an engine 202 to be mounted on a snowmobile 201 is set inclined forwards in an engine compartment 206 so as to reduce the full height of engine 202 while the aforementioned components are laid out in the space created by the inclined arrangement of the engine.
On the other hand, in order to enhance the power of a four-cycle engine which is relatively low in power compared to a two-cycle engine, it is generally known that a supercharger(so-called turbocharger) is provided on the intake side of the engine so as to increase the amounts of air and fuel to be supplied to the combustion chamber, to thereby enhance the engine power.
When the engine has a supercharger, provision of an intercooler in the intake line is effective in improving the intake efficiency. However, the position at which the intercooler is attached needs careful thought as to the cooling efficiency of the engine and is affected by the attached position of the supercharger, so that it has been very difficult to design the layout and allot mounting spaces for these components in the engine compartment.
For example, when the intercooler is arranged on the top of the engine, the full height of the engine becomes high so that the center of gravity as well as the body height of the snowmobile becomes high, hence the result is not preferable.
On the other hand, when the intercooler is arranged in front of the engine, the heavy part is located away from the center of gravity, so that the maneuverability lowers. Further, there is another drawback in that if the snowmobile is collided, the front part of the engine compartment will crush so that damage to the engine will become serious.
For a four-cycle engine, the oil pan, designated at 238, needs to be positioned at the engine bottom. If the engine is of a wet sump type, a large oil pan 238 is needed, which will cause difficulty of interference with the steering shaft, designated at 224, as shown in FIG. 2.
Further, for a snowmobile, the underside of the engine compartment serves as a sled sliding over snow, hence needs to be closed, which makes maintenance work such as changing oil difficult.
Moreover, when a four-cycle engine with a V-belt type automatic transmission is used for a snowmobile, the engine is used at higher speeds compared to that of a four-wheel vehicle. Therefore, the engine oil increases in temperature due to increased amount of heat from the engine, whereby oil film starvation may occur, leading to damage to the engine.
The present invention has been devised in view of the above conventional difficulties, it is therefore an object of the present invention to provide a snowmobile four-cycle engine arrangement with which space saving in the engine compartment is achieved and the workability of maintenance is improved. It is another object of the present invention to provide a snowmobile four-cycle engine arrangement with which cooling performance of the air and engine oil supplied to the engine is improved and space saving is achieved without any loss of maneuverability.
In order to achieve the above object, the present invention is configured as follows:
In accordance with the first aspect of the present invention, a snowmobile four-cycle engine arrangement includes: a four-cycle engine arranged in an engine compartment formed in the front body of a snowmobile with its crankshaft laid substantially parallel to the body width and having a cylinder portion inclined forwards with respect to the vehicle""s direction of travel, the engine employing a dry sump oil supplying system; and an oil tank provided in the engine compartment, separately from the engine.
In accordance with the second aspect of the present invention, the snowmobile four-cycle engine arrangement having the above first feature is characterized in that the oil tank is arranged in front of the engine and on the top of a front suspension housing which is projected upwards from the bottom of the engine compartment.
In accordance with the third aspect of the present invention, the snowmobile four-cycle engine arrangement having the above first feature is characterized in that the oil tank is arranged in the rear of the engine and on the upper face of a track housing which is projected upwards from the bottom of the engine compartment.
In accordance with the fourth aspect of the present invention, the snowmobile four-cycle engine arrangement having the above second feature is characterized in that the oil tank is arranged in the rear of the engine and on the upper face of a track housing which is projected upwards from the bottom of the engine compartment.
In accordance with the fifth aspect of the present invention, the snowmobile four-cycle engine arrangement having the above first feature is characterized in that the engine compartment has an opening port with a mating openable and closable lid element, at its bottom for creating communication between the inside of the engine compartment and the external space, at a position opposing the bottom of the oil pan of the engine.
In accordance with the sixth aspect of the present invention, the snowmobile four-cycle engine arrangement having the above second feature is characterized in that the engine compartment has an opening port with a mating openable and closable lid element, at its bottom for creating communication between the inside of the engine compartment and the external space, at a position opposing the bottom of the oil pan of the engine.
In accordance with the seventh aspect of the present invention, the snowmobile four-cycle engine arrangement having the above third feature is characterized in that the engine compartment has an opening port with a mating openable and closable lid element, at its bottom for creating communication between the inside of the engine compartment and the external space, at a position opposing the bottom of the oil pan of the engine.
In accordance with the eighth aspect of the present invention, the snowmobile four-cycle engine arrangement having the above fourth feature is characterized in that the engine compartment has an opening port with a mating openable and closable lid element, at its bottom for creating communication between the inside of the engine compartment and the external space, at a position opposing the bottom of the oil pan of the engine.
In accordance with the ninth aspect of the present invention, a snowmobile four-cycle engine arrangement includes: a four-cycle engine having a cylinder head on the top thereof and arranged in an engine compartment formed in the front body of a snowmobile with its crankshaft laid substantially parallel to the body width and its engine body inclined forwards with respect to the vehicle""s direction of travel; and an intake path on the upper face of the engine body, and is characterized in that a heat exchanger for cooling the engine cooling water, engine oil or air to be supplied to the engine is arranged in the tunnel created inside the body frame for accommodating a track for driving.
In accordance with the tenth aspect of the present invention, the snowmobile four-cycle engine arrangement having the above ninth feature is characterized in that the heat exchanger is disposed in front of the track, with respect to the vehicle""s direction of travel, inside the tunnel.
In accordance with the eleventh aspect of the present invention, the snowmobile four-cycle engine arrangement having the above ninth feature is characterized in that an intercooler for cooling the air to be supplied to the engine is put into use as the heat exchanger.
In accordance with the twelfth aspect of the present invention, the snowmobile four-cycle engine arrangement having the above tenth feature is characterized in that an intercooler for cooling the air to be supplied to the engine is put into use as the heat exchanger.
In accordance with the thirteenth aspect of the present invention, the snowmobile four-cycle engine arrangement having the above ninth feature is characterized in that an oil cooler for cooling the engine oil is put into use as the heat exchanger.
In accordance with the fourteenth aspect of the present invention, the snowmobile four-cycle engine arrangement having the above tenth feature is characterized in that an oil cooler for cooling the engine oil is put into use as the heat exchanger.
In accordance with the fifteenth aspect of the present invention, the snowmobile four-cycle engine arrangement having the above ninth feature is characterized in that a radiator for cooling the engine cooling water is put into use as the heat exchanger.
In accordance with the sixteenth aspect of the present invention, the snowmobile four-cycle engine arrangement having the above tenth feature is characterized in that a radiator for cooling the engine cooling water is put into use as the heat exchanger.
In accordance with the seventeenth aspect of the present invention, the snowmobile four-cycle engine arrangement having the above ninth feature is characterized in that an integrated configuration comprised of an oil cooler for cooling the engine oil and a radiator for cooling the engine cooling water is put into use as the heat exchanger.
In accordance with the eighteenth aspect of the present invention, the snowmobile four-cycle engine arrangement having the above tenth feature is characterized in that an integrated configuration comprised of an oil cooler for cooling the engine oil and a radiator for cooling the engine cooling water is put into use as the heat exchanger.
In accordance with the nineteenth aspect of the present invention, the snowmobile four-cycle engine arrangement having the above thirteenth feature is characterized in that a thermostat is interposed in the oil path of the oil cooler.
In accordance with the twentieth aspect of the present invention, the snowmobile four-cycle engine arrangement having the above fourteenth feature is characterized in that a thermostat is interposed in the oil path of the oil cooler.
In accordance with the twenty-first aspect of the present invention, the snowmobile four-cycle engine arrangement having the above seventeenth feature is characterized in that a thermostat is interposed in the oil path of the oil cooler.
In accordance with the twenty-second aspect of the present invention, the snowmobile four-cycle engine arrangement having the above eighteenth feature is characterized in that a thermostat is interposed in the oil path of the oil cooler.
According to the present invention, since the engine employs a dry sump oil supplying system, it is possible to make the engine body low in height. Since the oil tank is provided in the engine compartment, separately from the engine, it is possible to make efficient use of the space inside the engine compartment as well as to provide a compact engine arrangement.
Since the oil tank is arranged in front of the engine, on the upper surface of the front suspension housing, it is possible to attain space saving. Further, this arrangement allows the oil tank to receive little thermal influence from the engine and makes it possible to cool the engine oil effectively from the air flow during running.
Further, since the oil tank is arranged on the top face of the track housing in the rear of the engine, it is possible to achieve space saving as well as to dispose it apart from the heat source of the engine. Further, the oil tank can be cooled by snow powder stirred up during running, so that the engine oil can be cooled efficiently.
Since the engine compartment has an opening port with an openable and closable lid element for creating communication between the inside of the engine compartment and the external space, it is possible to make an access to the engine from the underside of the engine compartment when maintenance such as changing oil is needed, hence improve the workability.
According to the present invention, since the heat exchanger for cooling the engine cooling water, engine oil or air to be supplied to the engine is arranged in the tunnel created inside the body frame for accommodating a track for driving, it is possible to provide a snowmobile four-cycle engine arrangement in which the heat exchanger will not receive any thermal influence from the engine compartment and can be cooled markedly efficiently by snow powder stirred up during running. Further, provision of the heat exchanger outside the engine compartment makes it possible to reduce the engine height so realize deployment of a four-cycle engine. Further, this configuration enhances space saving in the engine compartment and is markedly effective in reducing the body height so avoid any loss of maneuverability.
Since the heat exchanger is disposed in front of the track, with respect to the vehicle""s direction of travel, in the tunnel, it is possible to arrange it close to, and approximately below, the engine. Therefore, the connections such as pipes, etc., can be shortened, thus making it possible to simplify the communication paths so reduce the cost.
Since the intercooler for cooling the air to be supplied to the engine is put into use as the heat exchanger, it is possible to efficiently cool the air which has been compressed and sent from the supercharger and hence is high in temperature to thereby improve the engine power.
Since the oil cooler for cooling the engine oil is put into use as the heat exchanger, it is possible to efficiently cool the engine oil which is high in temperature. Therefore, it is possible to prevent oil film starvation hence prevent damage to the engine to thereby maintain the engine in a good running state.
Since the radiator for cooling the engine cooling water is put into use as the heat exchanger, it is possible to efficiently cool the cooling water which is high in temperature. Therefore, it is possible to prevent the engine from overheating so keep the engine in a good running state.
Since the oil cooler for cooling the engine oil and the radiator for cooling the engine cooling water are integrated as the heat exchanger, it is possible to eliminate the necessity of providing an oil cooler and radiator separately hence achieve space saving and reduce the number of parts.
Since a thermostat is interposed in the oil path of the oil cooler, the engine oil can be kept at a proper temperature. Therefore, it is possible to prevent the engine oil from being excessively cooled, hence keep the engine in a good running state.